Radar data from the Cassini spacecraft have revealed regional variations amongst sand dunes on Titan, the largest moon of Saturn.
Dune fields are common on Titan and cover about 13 % of this giant moon, stretching over 10 million km2. They are gigantic by Earthly standards, measuring hundreds of kilometers long, 1–2 km wide and around 100 m high.
Titan's Belet dune field (NASA / JPL / Caltech / ASI / ESA / USGS / ESA)
According to the European Space Agency, with data from the Cassini spacecraft, an international team of researchers found that the size of Titan’s dunes is controlled by at least two factors: altitude and latitude. Their findings appear in the January issue of the journal Icarus.
Titan's Belet dune field (NASA / JPL / Caltech / ASI / ESA / USGS / ESA)
Sand on Titan is made of solid hydrocarbons that precipitate out of the atmosphere and then aggregate into millimeter-sized grains by a still unknown process.
The main dune fields on Titan are found in lowland areas. Dunes at higher elevations tend to be narrower and more widely separated, and the gaps between them appear brighter to Cassini’s radar, indicating a thinner covering of sand.
In terms of latitude, the dunes on Titan are confined to its equatorial region. However, they tend to become narrower and more widely spaced at northern latitudes. The researchers suggest that this may be due to Saturn’s elliptical orbit.
Titan's Fensal dune field (NASA / JPL / Caltech / ASI / ESA / USGS / ESA)
“As one goes to the north, the soil moisture probably increases, making the sand particles less mobile and, as a consequence, the development of dunes more difficult,” said Dr. Alice Le Gall, lead author on the study and a researcher at Jet Propulsion Laboratory in Pasadena, California and at Laboratoire Atmosphères, Milieux, Observations Spatiales, France.
“Understanding how the dunes form as well as explaining their shape, size and distribution on Titan’s surface is of great importance to understanding Titan’s climate and geology,” explained Nicolas Altobelli, Cassini–Huygens project scientist.
“As their material is made out of frozen atmospheric hydrocarbons, the dunes might provide us with important clues on the still puzzling methane/ethane cycle on Titan, comparable in many aspects with the water cycle on Earth,” concluded Mr. Altobelli.
